To generate dsa key

Generate 4096 bits rsa key

Default key is 2048 bits which is generally sufficient. In case you need 4096 bits keys use the following command.

$ ssh-keygen -t rsa -b 4096

Generate rsa key with comment

Comment gets appended to the public key as shown below. This is useful in case you are generating key for some other user and want to have relevant comment. This may also be useful for maintaining multiple keys.